If the incident does turn out to be motivated by anti-Islamic sentiment, it would be one of dozens of such events that happen each year, according to the FBI's Uniform Crime Reports program. Prior to the 9/11 attacks, the program typically recorded between 20 and 30 anti-Muslim hate crimes per year. But in 2001 that number rose more than tenfold to nearly 500. In the years since, annual hate crimes against Muslims have consistently hovered in the 100-150 range, roughly five times higher than the pre-9/11 rate.

These figures are almost certainly an undercount, given that participation in the program is voluntary, and some state and local police departments do a better job of tracking this data than others. Overall, anti-Muslim crimes now make up about 13 percent of religiously-motivated hate crimes, and 2 percent of all hate crimes in general.

It should be noted that Jews are consistently targeted for their faith more often than members of any other religious group, and that anti-Semitic crimes accounted for roughly 60 percent of religious hate crimes last year. Muslims are the second-most frequently targeted. Despite public opinion polling consistently showing that Americans mistrust atheists just as much as Muslims, anti-atheist hate crimes are rare.

But religiously motivated murders are rare. too. There are no such killings listed in the FBI's database for 2013. Most hate crimes involve assault, intimidation or vandalism. If the Chapel Hill killings do turn out to be religious in nature, they would be a tragic exception to the general rule.

Religious tension in this country traditionally hasn't reached the level of racial tension that accompanied the police shootings of unarmed black men this past year. This fact is reflected in the hate crime statistics as well. Racially-motivated hate crimes outnumber religiously-motivated crimes by roughly two to one.

But the fact that crimes against Muslims remain high compared to their pre-9/11 levels indicates we have plenty of work to do on the religious front as well.

Christopher IngrahamChristopher Ingraham writes about all things data. He previously worked at the Brookings Institution and the Pew Research Center. Follow